1. Field of the Invention
The present invention relates to novel 1,5-diethenylnaphthalene compounds, to a process for the preparation thereof, and to the conversion of same via reaction with an organic alkali metal compound into bifunctional primers for anionic polymerization mechanisms.
2. Description of the Prior Art
Organic alkali metal compounds, such as organodilithium compounds, are known to this art as especially advantageous bifunctional primers for anionic polymerization reactions, since the three-step procedure required to prepare ABA sequenced copolymers by monofunctional priming is reduced by one step through the use of bifunctional primers. These latter are also important in copolymerization reactions, when the second monomer cannot re-initiate polymerization of the first.
Numerous sequenced copolymers have been prepared using alkali metal naphthalides as bifunctional primers. These bifunctional primers are efficacious only in polar reaction media, such a tetrahydrofuran, in particular for the polymerization of diene monomers. However, they cannot provide a polydiene microstructure having a high degree of 1,4-configuration (cis- or trans-).
In the event that a special microstructure, in general a 1,4-cis addition for polydienes, is desired, the anionic polymerization must be carried out in a nonpolar solvent utilizing the alkali metal, e.g., lithium, as the counter-ion. Unfortunately, and probably because of associated reagents, organic alkali metal compounds, such as organodilithium compounds, exhibit a low level of solubility in hydrocarbonaceous solvents. Tests for increased solubility using very small amounts of ether or amines indicated that these additives affect the microstructure of the diene block. The disadvantage presented by the seeding technique is a high dispersion index for the central sequence.
To date, many compounds have been described for their possible use as bifunctional lithium-containing primers which are soluble in nonpolar solvents.
For example, U.S. Pat. No. 4,200,718, at column 14, describes the compound corresponding to the formula: 
which is reacted with secondary butyllithium to prepare [2,7-naphthalenediylbis(3-methyl-1-phenylpentylidene]-bis(lithium), a primer used for the anionic polymerization of butadiene.
Turgut Nugay and Savas Kucukyavuz, in Polym. International, 29, 195 (1992), describe the preparation of 1,5-diethenylnaphthalene and reaction thereof with secondary butyllithium in n-heptane, in the absence of any polar additive, thereby producing 1,5-bis(1-lithio-3-methylpentyl)naphthalene. This compound was easily isolated and the soluble monofunctional compounds removed. When dissolved in benzene (solubility: 3.2xc3x9710xe2x88x922 mole/liter), it was used a primer for the sequenced copolymeriztion of isoprene and styrene.
Nonetheless, need continues to exist to provide even better solubility in nonpolar solvents and enhanced control over the bifunctionality of such 1,5-bisubstituted naphthalene-containing primers.
Accordingly, a major object of the present invention is the provision of novel 1,5-diethenylnaphthalene compounds that avoid or conspicuously ameliorate the above disadvantages and drawbacks to date characterizing the state of this art.
Briefly, the present invention features compounds having the formula (I): 
in which R1 is a linear, branched, or cyclic alkyl radical having from 1 to 12 carbon atoms, or a substituted or unsubstituted aryl radical.
The alkyl radicals R1 are preferably methyl radicals; the aryl radicals R1 are preferably phenyl radicals.
The present invention also features a process for preparing the compounds (1), comprising, in a first step, reacting a compound having the formula (II): 
with a compound having the formula (III):
R1xe2x80x94Mxe2x80x83xe2x80x83(III)
in which R1 is as defined above; and M is an alkali metal or Mxe2x80x2Hal (Mxe2x80x2 representing an alkaline earth metal, and Hal, a halogen), thereafter hydrolyzing the derivative thus formed to provide a compound having the formula (IV): 
and, in a second step, dehydrating the compound having formula (IV), thereby providing the desired final product.
More particularly according to the present invention, in the first step of the process aspect thereof, to add the organometallic compound (III) to the compound (II), the respective reagents are employed in amounts of at least two moles of compound (III) per 1 mole of compound (II), preferably using an amount of compound (III) slightly in excess of the stoichiometric amount, such addition being carried out in an aprotic solvent medium (e.g., tetrahydrofuran, toluene, ethyl ether, benzene, ethylbenzene, cyclohexane, and mixtures thereof), the temperature being regulated depending on the reagents used, and the reaction time being approximately 6 to 24 hours. This reaction is followed by hydrolysis carried out under conditions resulting in the deactivation of the reaction product, whether by means of methanol acidified with acetic acid or via the use of a water/ice/hydrochloric acid mixture.
The second step entailing dehydration can be carried out, for example, in an acetic acid/sulfuric acid medium concentrated under reflux, the proportion of sulfuric acid in comparison with the acetic acid being 0.1% to 5% by weight; or in a toluene/paratoluene sulfonic acid medium.
The present invention also features a bifunctional primer, namely, of the product of the reaction of the compound of formula (I), as indicated above, with a compound having the formula (V):
R2xe2x80x94Mxe2x80x3xe2x80x83xe2x80x83(V)
in which Mxe2x80x3 is an alkali metal, notably lithium or sodium; and R2 is a C1-C6 alkyl radical, a C5-C12 cycloalkyl radical or an aromatic radical, with the proviso that the compound (V) can be an anionic polymer comprising a terminal carbanion R2 and the counter-ion Mxe2x80x3, said bifunctional primer being represented by the following formula (IV): 
in which R2 preferably is a secondary butyl group.
When Mxe2x80x3 represents Li and when the organolithium compound (V) is an anionic polymer, thus affording a bifunctional primer providing star-shaped polymers, the polymeric carbanion R2 may be a vinylaromatic polymer carbanion, such as polystyrene and poly(alpha-methylstyrene), or a diene-containing polymer carbanion such as polybutadiene and polyisoprene.
The bifunctional primer is synthesized by reacting compounds (I) and (V) in amounts of at least 2 moles of compound (V) per 1 mole of compound (I), in particular utilizing a slight excess of compound (V) as compared with the stoichiometric amount in a purified aprotic solvent medium (examples of solvents are provided above with reference to the addition of the organometallic compound (III) to compound (II)), with the subsequent polymerization being carried out by the direct addition of monomers to the reaction medium. A slight excess of compound (V) gives rise to deactivation of the residual protic impurities in the reaction medium.
Too, the present invention features a process for anionic polymerization of at least one polymerizable monomer with an alkali metal compound employed as the primer, this process being characterized in that the primer used is a bifunctional primer, as indicated above.
By xe2x80x9cpolymerizable monomersxe2x80x9d are intended diene-containing, vinylaromatic, and (meth)acrylic monomers.
By the expression xe2x80x9cdiene-containing monomerxe2x80x9d is intended a diene selected from among conjugated linear or cyclic dienes having from 1 to 20 atoms of carbon. Exemplary thereof are butadiene, isoprene, 1,3-pentadiene, cyclopentadiene, and 6,7,8,9-tetrahydroindene. The preferred monomers are butadiene and isoprene.
By the term xe2x80x9cvinylaromaticxe2x80x9d monomers are intended ethylenically-unsaturated aromatic monomers. Exemplary thereof are styrene, vinyltoluene, alpha-methylstyrene, 4-methylstyrene, 3-methylstyrene, 4-ethylstyrene, 3,4-dimethylstyrene, 3-tert-butylstyrene, and 2-vinylnaphthalene. Hydroxylated styrene derivatives can also be employed, such as 4-methoxystyrene, 2-hydroxymethylstyrene, and 4-ethoxystyrene, provided that the OH function is protected. The preferred monomer is styrene.
By the term xe2x80x9c(meth)acrylic monomerxe2x80x9d is intended a monomer selected from among the (meth)acrylates having the following respective formulae: 
in which Re is a linear or branched, primary, secondary, or tertiary C1-C18 alkyl radical, a C5-C18 cycloalkyl radical, a (C1-C18 alkoxy) C1-C18 alkyl radical, a (C1-C18 alkylthium) C1-C18 alkyl radical, and aryl and aralkyl radicals, these radicals optionally being substituted by at least one atom of halogen and/or at least one hydroxyl group after protecting this hydroxyl group, said alkyl groups being linear or branched, glycidyl, norbornyl, isonorbornyl (meth)acrylates, and di-(C1-C18 alkyl)-(meth)acrylamides.
Exemplary methacrylates having the above formula include methyl, ethyl, 2,2,2-trifluoroethyl, n-propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, n-amyl, 1-amyl, n-hexyl, 2-ethylhexyl, cyclohexyl, octyl, 1-octyl, nonyl, decyl, lauryl, stearyl, phenyl, and benzyl methacrylates. The preferred methacrylic monomer is methyl methacrylate.
Exemplary acrylates having the above formula include methyl, ethyl, n-propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, hexyl, 2-ethylhexyl, isooctyl, 3,3,5-trimethyhexyl, nonyl, isodecyl, lauryl, octadecyl, cyclohexyl, phenyl, methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl acrylates.
In general, in a step carried out following preparation of an active polymer sequence, when such sequence is formed from at least one vinylaromatic and/or diene-containing monomer, the latter may be reacted with at least one vinylaromatic, (meth)acrylic, or diene-containing monomer, if required in the presence of a ligand, in order to obtain a trisequenced copolymer. This ligand may be selected, on the one hand, from among the alkali metal or alkaline earth metal salts, e.g., chlorides, fluorides, bromides, iodides, borides, and, on the other, among the alkali metal organic salts, e.g., alcoholates.
Illustrative thereof is, in particular, the anionic polymerization of at least one diene monomer in the presence of a nonpolar solvent, e.g., toluene, benzene, ethylbenzene, and mixtures thereof, as required with a small amount of cyclohexane. After preparing the active polydiene-containing sequence, this sequence may be reacted with at least one vinylaromatic or (meth)acrylate monomer, if necessary in the presence of a ligand such as described in published French Patent Application No. 92/14,318, to produce a trisequenced copolymer.
Also illustrative is the production of trisequenced poly (methyl methacrylate)/vinylaromatic or diene-containing polymer/poly(methyl methacrylate) polymers.
Typically, polymerization of a diene-containing monomer is carried out at a temperature ranging from xe2x88x9280xc2x0 C. to +100xc2x0 C., and, preferably, at a temperature ranging from xe2x88x9270xc2x0 C. to +70xc2x0 C., and polymerization of a (meth)acrylate monomer is carried out at a temperature ranging from xe2x88x9280xc2x0 C. to +60xc2x0 C. and, preferably, at a temperature ranging from xe2x88x9270xc2x0 C. to +20xc2x0 C. The polymerization of a vinylaromatic monomer is typically carried out at a temperature ranging from xe2x88x9280xc2x0 C. to +100xc2x0 C., and, preferably, at a temperature ranging from xe2x88x9270xc2x0 C. to +70xc2x0 C.
The polymerization of a diene-containing monomer is normally carried out over a time period of xc2xd hour to 24 hours; polymerization of a (meth)acrylate monomer is carried out over a period of time of less than 1 hour, and that of a vinylaromatic monomer, between xc2xd hour and 24 hours.
The protonic compounds introduced at the end of polymerization to deactivate the active polymer sites may be selected from among water, alcohols, and acids. A preferred such material is acidified methanol.
Subsequently, it is possible to at least partially reduce the residual unsaturation of the polydiene sequences via conventional hydrogenation techniques, to improve various of the properties thereof, in particular stability vis-a-vis ultraviolet light.
The trisequenced (co)polymers and copolymers, such as those prepared using the bifunctional primer according to the invention, are useful for such well known applications as elastomers, thermoplastic elastomers, compatibility-enhancing agents, etc. As thermoformable materials, they may be converted by techniques such as extrusion and injection molding, to provide shaped articles such as fibers, coatings and coverings, shoes, etc. The aforesaid sequenced copolymers, in which the methacrylic monomer is methyl methyacrylate having a high degree of heat-resistance, can be used as pressure-sensitive adhesives and as agents for enhancing the shock- and heat-resistance of polymers, as described in published French Patent Application No. 92/14,318.